1. Field of the Invention
This invention relates to a control apparatus for a transmission as controls the transmission carried on an automobile or the like vehicle. More particularly, it relates to a control apparatus for a transmission in which a speed change control is performed by a motor.
2. Description of the Related Art
Heretofore, there has been known a transmission which is carried on an automobile or the like vehicle and in which a speed change control is performed by a motor. The transmission carries out a speed change in such a way that, in a twin-clutch type transmission, a shift fork is manipulated by two motors, thereby to select a gear which transmits power (refer to, for example, Patent Document 1 being JP-A-2007-177878, Sector 0018 and FIG. 1).
Besides, a technique for estimating the coil temperature of a motor has heretofore been known. More specifically, a predetermined voltage is applied across motor terminals immediately after the stop of the drive of the motor, the coil resistance value of the motor is calculated from the applied voltage and a current which flows through the motor at that time, and the coil temperature of the motor is estimated using the calculated coil resistance of the motor and the coil temperature characteristic of the motor (refer to, for example, Patent Document 2 being JP-A-2005-151790, Column of Abstract and FIG. 2).
In a control apparatus for a transmission as controls the transmission which carries out the speed change by the motors, like the related art transmission disclosed in Patent Document 1, when speed changes occur frequently on account of sport traveling or the like, currents frequently flow through the coils of the motors (hereinbelow, termed “motor coils”), and the temperatures of the motor coils rise. When currents are caused to flow through the motors by further continuing speed changes in this state, the temperatures of the motor coils reach a critical temperature, to pose the problem that the motor coils burn.
Besides, in a case where the speed change is carried out by utilizing the motor, one motor needs to be driven a plurality of times for one time of speed change. Therefore, in a case where the temperature detection technique for a motor coil as disclosed in Patent Document 2 is applied to a control apparatus for a transmission, a plurality of temperature measurements are performed for one time of speed change, thereby to pose the problem that a power consumption enlarges. Further, since the plurality of temperature measurements are performed, there is the problem that the temperature rise of the motor oil enlarges due to currents flowing in the temperature measurements, leading to the burning of the motor coil.